1. Field of the Invention
The present invention generally relates to a substrate-supporting device configured to be installed in a CVD apparatus for forming a thin film on a substrate. The present invention also relates to a CVD apparatus in which the substrate-supporting device is installed.
2. Description of the Related Art
FIG. 1 is a schematic diagram of a conventional plasma CVD apparatus. The plasma CVD apparatus 1 comprises a reaction chamber 6, a gas inlet port 5, and a second electrode composed of a susceptor 3 which serves as a supporting portion and a heater 2. From a gas line which is not shown, a gas is introduced through the gas inlet port 5. A circular first electrode 9 is disposed just below the gas inlet port 5. The first electrode 9 has a hollow structure, and a number of fine pores provided on the bottom surface from which the gas is jetted out to a wafer which is a workpiece. Additionally, the first electrode 9 is configured to be replaceable with a shower plate 11 having multiple gas inlet holes for facilitating maintenance and reducing component costs.
Additionally, at the bottom of the reaction chamber 6, an exhaust port 10 is provided exhaust port 10 is joined with an external vacuum pump which is not shown, through which inside the reaction chamber 6 is exhausted. The susceptor 3 is disposed parallel to facing the first electrode 9. The susceptor 3 supports a wafer 4 on it and heats the wafer continuously by the heater 2 to maintain it at a given temperature (−50° C. to 650° C. The gas inlet port 5 and the first electrode 9 are insulated from the reaction chamber 6 and connected to an external first radio-frequency power source 7. A second radio-frequency source 8 may also be connected at this time.
The susceptor 3 is generally made of aluminum or aluminum alloy, and the surface is constituted by an anodized oxide film to provide a protective coat. As is conventionally known, wafer sticking occurs if the susceptor having this construction is used; therefore, for the purpose of reducing a contact area of a wafer and a susceptor, measures such as blasting, blasting+chemical treatment (some etching), blasting+polishing (Japanese Patent Laid-open No. 1998-340896) and providing regions of high elevation on a susceptor surface (U.S. Pat. No. 5,531,835) are taken.